Among the most common fatal diseases are vascular diseases, in particular cardiac infarction. This is caused by disease of the coronary vessels (atherosclerosis). Deposits (atherosclerotic plaque) thereby cause a blockage of the coronary vessels.
If coronary angiography shows severe restriction (stenosis) in the coronary vessels, which causes angina pectoris, restricts performance and/or threatens the life of the patient, in the majority of cases today a PTCA (Percutaneous Transluminal Coronary Angioplasty) is carried out. To this end the restrictions in the coronary vessels are dilated with the so-called balloon catheter.
The action mechanism of conventional balloon angioplasty for lumen gain is based on the one hand on compression of the plaque and on the other hand on rearrangement of the non-compressible plaque, components by dissection of the vessel intima and media and over-dilation of the circumference of the vessel. Compression of large quantities of plaque can result in damage to the inner wall of the vessel, which leads to an increase in the restenosis rate.
The use of a stent in the expanded segment of the vessel can reduce the restenosis rate. Stent implantation prevents structural changes in the vessel due to the mechanical restoring force of the stent. A clear disadvantage of the method is the additional process step and the additional cost of the stent.
The cutting balloon is a special balloon holding three or four small blades depending on size. When the balloon opens, these become aligned and make longitudinal cuts in the vessel deposits or “shave” plaque from the vessel wall, before the coronary artery is dilated by the balloon.
The object of this technique is to reduce or even eliminate the elastic restoring forces, to achieve a larger vessel diameter after dilation. It also prevents irregular tearing of the vessel intima, which could be responsible for acute occlusions after balloon dilation. Studies show that hyperplasia (inflammation response with swelling) of the intima can be reduced after balloon dilation and the restenosis rate is thus significantly reduced by use of the cutting balloon.
A device according to the cutting balloon principle is for example disclosed in WO 82/04388, “Coronary Cutting and Dilating Instrument” and in WO 02/078511 “Inflatable Medical Device with Combination Cutting Elements and Drug Delivery Conduits”. A known product is for example the Cutting Balloon Ultra from Boston Scientific, MA, USA.
The intervention described above is carried out subject to X-ray control using contrast agents with an angiograph device. The disadvantage of this method is that the coronary vessels are only displayed as two-dimensional and only the actual constriction is shown in the X-ray image. During the intervention it is difficult for medical personnel to distinguish between plaque and vascular wall. This increases the risk that the blades of the balloon might cut in the wrong place or the cuts might be too deep (deep vessel wall injury).
The problem is described for example in the document “Impact of Deep Vessel Injury on Acute Response and Remodeling of Coronary Artery Segments After Cutting Balloon Angioplasty”, Mamoo Nakamura, The American Journal of Cardiology Vol. 91, Jan. 1, 2003.
Insertion of an IVUS catheter (Intravascular Ultrasound) into the vessel improves the imaging information but has the disadvantage that a relatively expensive catheter also has to be inserted into the patient and must be removed from the vessel before insertion of the balloon catheter. An IVUS system is for example disclosed in EP 0 885 594 B1 and in U.S. Pat. No. 5,193,546. The disadvantage of the IVUS solution is the limited spatial resolution of the ultrasound method.
Significantly better spatial resolution, in particular in the relevant close-up range, could be provided by an OCT catheter, which is inserted separately into the vessel.
The OCT method is for example disclosed in WO 01/11409 A2, in U.S. Pat. No. 5,921,926 and in EP 0 815 801 B1. The OCT technique operates in a similar fashion to imaging ultrasound (B mode). The essential physical principle is based on the Michelson interferometer.
The disadvantage of this method is that the OCT device has to be withdrawn from the vessel whenever the cutting balloon is inserted.